.\" Copyright (C) Tom Bjorkholm & Markus Kuhn, 1996
.\"
.\" %%%LICENSE_START(GPLv2+_DOC_FULL)
.\" This is free documentation; you can redistribute it and/or
.\" modify it under the terms of the GNU General Public License as
.\" published by the Free Software Foundation; either version 2 of
.\" the License, or (at your option) any later version.
.\"
.\" The GNU General Public License's references to "object code"
.\" and "executables" are to be interpreted as the output of any
.\" document formatting or typesetting system, including
.\" intermediate and printed output.
.\"
.\" This manual is distributed in the hope that it will be useful,
.\" but WITHOUT ANY WARRANTY; without even the implied warranty of
.\" MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
.\" GNU General Public License for more details.
.\"
.\" You should have received a copy of the GNU General Public
.\" License along with this manual; if not, see
.\" <http://www.gnu.org/licenses/>.
.\" %%%LICENSE_END
.\"
.\" 1996-04-01 Tom Bjorkholm <tomb@mydata.se>
.\"            First version written
.\" 1996-04-10 Markus Kuhn <mskuhn@cip.informatik.uni-erlangen.de>
.\"            revision
.\" Modified 2004-05-27 by Michael Kerrisk <mtk.manpages@gmail.com>
.\"
.TH SCHED_SETPARAM 2 2016-10-08 "Linux" "Linux Programmer's Manual"
.SH NAME
sched_setparam, sched_getparam \- set and get scheduling parameters
.SH SYNOPSIS
.nf
.B #include <sched.h>
.sp
.BI "int sched_setparam(pid_t " pid ", const struct sched_param *" param );
.sp
.BI "int sched_getparam(pid_t " pid ", struct sched_param *" param );
.sp
\fBstruct sched_param {
    ...
    int \fIsched_priority\fB;
    ...
};
.fi
.SH DESCRIPTION
.BR sched_setparam ()
sets the scheduling parameters associated with the scheduling policy
for the process identified by \fIpid\fP.
If \fIpid\fP is zero, then
the parameters of the calling process are set.
The interpretation of
the argument \fIparam\fP depends on the scheduling
policy of the process identified by
.IR pid .
See
.BR sched (7)
for a description of the scheduling policies supported under Linux.

.BR sched_getparam ()
retrieves the scheduling parameters for the
process identified by \fIpid\fP.
If \fIpid\fP is zero, then the parameters
of the calling process are retrieved.

.BR sched_setparam ()
checks the validity of \fIparam\fP for the scheduling policy of the
thread.
The value \fIparam\->sched_priority\fP must lie within the
range given by
.BR sched_get_priority_min (2)
and
.BR sched_get_priority_max (2).

For a discussion of the privileges and resource limits related to
scheduling priority and policy, see
.BR sched (7).

POSIX systems on which
.BR sched_setparam ()
and
.BR sched_getparam ()
are available define
.B _POSIX_PRIORITY_SCHEDULING
in \fI<unistd.h>\fP.
.SH RETURN VALUE
On success,
.BR sched_setparam ()
and
.BR sched_getparam ()
return 0.
On error, \-1 is returned, and
.I errno
is set appropriately.
.SH ERRORS
.TP
.B EINVAL
Invalid arguments:
.I param
is NULL or
.I pid
is negative
.TP
.B EINVAL
.RB ( sched_setparam ())
The argument \fIparam\fP does not make sense for the current
scheduling policy.
.TP
.B EPERM
.RB ( sched_setparam ())
The calling process does not have appropriate privileges
(Linux: does not have the
.B CAP_SYS_NICE
capability).
.TP
.B ESRCH
The process whose ID is \fIpid\fP could not be found.
.SH CONFORMING TO
POSIX.1-2001, POSIX.1-2008.
.SH NOTES
.PP
Scheduling parameters are in fact per-thread
attributes on Linux;
see
.BR sched (7).
.SH SEE ALSO
.ad l
.nh
.BR getpriority (2),
.BR nice (2),
.BR sched_get_priority_max (2),
.BR sched_get_priority_min (2),
.BR sched_getaffinity (2),
.BR sched_getscheduler (2),
.BR sched_setaffinity (2),
.BR sched_setattr (2),
.BR sched_setscheduler (2),
.BR setpriority (2),
.BR capabilities (7),
.BR sched (7)
